TELEPHONE CHANNEL CONNECTION CIRCUIT FOR NETWORK CONTROL DEVICE

摘要

PURPOSE:To avoid the bell ringing for the telephones on the same circuit when a power source is applied to a data transmitting equipment, by providing a transistor circuit consisting of a transistor, a resistance, a capacitor and a diode between a subscriber telephone side and the data transmitting equipment side. CONSTITUTION:A telephone switchboard reverse the polarity between the terminals 1 and 2 to start a data transmitting equipment. The terminal 1 is connected to the collector of a switching transistor TR and the anode of a diode RC. Then the base of the TR is connected to a resistor R and a capacitor C of a charging circuit; the other end of the R is connected to the base of the TR; the emitter of the TR is connected to the terminal 3; and the terminal 2 is connected to the other end of the C and the terminal 4 respectively. When a start is given from a telephone switchboard, the voltage of the TR base varies by the CR time constant. And the larger the CR time constant, the more the both-end voltages of a load RL changes gradually. Thus a bell ring caused by a sudden change of the voltage between the terminals 1 and 2 is avoided.